For adhesives, sealing materials, and the like, a paste sol is prepared, and the sol is used for coating, painting, construction, mixing, and the like. When the paste sol cannot include a filler in a large amount due to the physical quality of a cured product of the sol, such a paste sol employs a filler capable of imparting high viscosity to the sol in a small amount, such as fumed silica.
The fumed silica exhibits excellent thixotropic properties but has a problem of causing extreme change in viscosity depending on a very small variation in the amount added.
Meanwhile, calcium carbonate is used as a filler for various polymer materials such as plastics, rubbers, inks, paints, sealing materials, PVC sols, and acrylic sols. Therefore, if the addition of calcium carbonate can impart excellent thixotropic properties, such a calcium carbonate can be used as a relatively inexpensive thixotropic property imparting agent.
Patent Document 1 discloses a surface-treated calcium carbonate of which surface is treated with an unsaturated fatty acid and a saturated fatty acid in a predetermined mixing ratio. When the surface-treated calcium carbonate is used and added to inks, paints, sealing materials, PVC sols, acrylic sols, and the like, excellent thixotropic properties can be imparted to the materials.
However, from the viewpoints of environmental health and the like, the reduction of the amount of an adhesion imparting agent and the like has recently been considered. The use of the surface-treated calcium carbonate in the related art achieves excellent thixotropic properties, but when an adhesion imparting agent is used in a reduced amount, a cured product from such a material has poor mechanical properties and especially has poor tensile properties. Therefore, there is a demand for a surface-treated calcium carbonate achieving high viscosity and excellent thixotropic properties and capable of imparting good mechanical properties to a cured product from such a material. As the physical properties and qualities of the cured products of an adhesive and a sealant, the mechanical properties are also important properties for the adhesive and the sealant. The tensile strength and the like are strictly regulated under ISO standards and Japanese Industrial Standards and sufficiently high performance is desired.
Patent Documents 2 to 14 disclose surface-treated calcium carbonates for imparting high viscosity and excellent thixotropic properties. Even when the surface-treated calcium carbonate disclosed in the related art is used, a cured product from the material has poor mechanical properties and poor adhesion properties, and it has been difficult to impart sufficient mechanical properties and sufficient adhesion properties to the cured product.
Patent Document 15 discloses a calcium carbonate having a surface treated with a surface treating agent containing lauric acid and myristic acid in an amount of 85% or more. However, even when such a surface-treated calcium carbonate is used, it has been difficult to impart high viscosity and excellent thixotropic properties.
In general, when a calcium carbonate surface is surface treated with a fatty acid, a paste sol curable resin composition containing the calcium carbonate obtains improved viscosity properties but the use of the fatty acid adversely affects a cured product of the composition to have poor mechanical properties and poor adhesion properties.